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The degree to which climate warming will stimulate soil organic carbon (SOC) losses via heterotrophic respiration remains uncertain, in part because different or even opposite microbial physiology and temperature relationships have been proposed in SOC models. We incorporated competing microbial carbon use efficiency (CUE)–mean annual temperature (MAT) and enzyme kinetic–MAT relationships into SOC models, and compared the simulated mass‐specific soil heterotrophic respiration rates with multiple published datasets of measured respiration. The measured data included 110 dryland soils globally distributed and two continental to global‐scale cross‐biome datasets. Model–data comparisons suggested that a positive CUE–MAT relationship best predicts the measured mass‐specific soil heterotrophic respiration rates in soils distributed globally. These results are robust when considering models of increasing complexity and competing mechanisms driving soil heterotrophic respiration–MAT relationships (e.g., carbon substrate availability). Our findings suggest that a warmer climate selects for microbial communities with higher CUE, as opposed to the often hypothesized reductions in CUE by warming based on soil laboratory assays. Our results help to build the impetus for, and confidence in, including microbial mechanisms in soil biogeochemical models used to forecast changes in global soil carbon stocks in response to warming. [ABSTRACT FROM AUTHOR]

In 1999, the Grain for Green Project was implemented by the Chinese government. Since then, the vegetation of Zuli River Basin, a semi-arid river basin of the Chinese Loess Plateau, has been greatly changed. Clearly understanding the impact of natural and artificial factors on vegetation change is important for policy making and ecosystem management. In this study, spatio-temporal variations in vegetation cover in Chinese Zuli River Basin during 1999–2016 were investigated using Landsat normalized difference vegetation index (NDVI) data. Analyses of several indicators, including changes in NDVI in different slopes and land use changes and the relationships between climatic factors and NDVI change, were presented to quantitatively evaluate the effects of agriculture, climate, and policy on NDVI change. The NDVI in the Zuli River Basin increased during the study period, and the main contributors to this change were forest in 1999–2011, cropland, abandoned farmland, and grassland in 2009–2016, and land with slopes ≤ 15°. Land with slope > 15°, where the "Project" was implemented, slightly contributed to the increase in regional NDVI. In 1999–2011, the project (−98.16%) combined with climate change (−68.18%) showed negative effects on the increase in NDVI in the Zuli River Basin, but agriculture (22.28%) played a positive role in increasing this index. In 2009–2016 and 1999–2016, the project (38.45% and 35.25%, respectively), the project combined with climate change (49.83% and 46.30%, respectively), agriculture (18.61% and 23.30%, respectively), promoted increases in NDVI in the basin. [ABSTRACT FROM AUTHOR]

Past vegetation and climatic conditions are known to influence current biodiversity patterns. However, whether their legacy effects affect the provision of multiple ecosystem functions, that is, multifunctionality, remains largely unknown. Here we analyzed soil nutrient stocks and their transformation rates in 236 drylands from six continents to evaluate the associations between current levels of multifunctionality and legacy effects of the Last Glacial Maximum (LGM) desert biome distribution and climate. We found that past desert distribution and temperature legacy, defined as increasing temperature from LGM, were negatively correlated with contemporary multifunctionality even after accounting for predictors such as current climate, soil texture, plant species richness, and site topography. Ecosystems that have been deserts since the LGM had up to 30% lower contemporary multifunctionality compared with those that were nondeserts during the LGM. In addition, ecosystems that experienced higher warming rates since the LGM had lower contemporary multifunctionality than those suffering lower warming rates, with a ~9% reduction per extra degree Celsius. Past desert distribution and temperature legacies had direct negative effects, while temperature legacy also had indirect (via soil sand content) negative effects on multifunctionality. Our results indicate that past biome and climatic conditions have left a strong "functionality debt" in global drylands. They also suggest that ongoing warming and expansion of desert areas may leave a strong fingerprint in the future functioning of dryland ecosystems worldwide that needs to be considered when establishing management actions aiming to combat land degradation and desertification. [ABSTRACT FROM AUTHOR]

Understanding under which climate and soil conditions the plant productivity–precipitation relationship is linear or nonlinear is useful for accurately predicting the response of ecosystem function to global environmental change. Using long-term (2000–2016) net primary productivity (NPP)–precipitation datasets derived from satellite observations, we identify > 5600 pixels in the North Hemisphere landmass that fit either linear or nonlinear temporal NPP–precipitation relationships. Differences in climate (precipitation, radiation, ratio of actual to potential evapotranspiration, temperature) and soil factors (nitrogen, phosphorous, organic carbon, field capacity) between the linear and nonlinear types are evaluated. Our analysis shows that both linear and nonlinear types exhibit similar interannual precipitation variabilities and occurrences of extreme precipitation. Permutational multivariate analysis of variance suggests that linear and nonlinear types differ significantly regarding to radiation, ratio of actual to potential evapotranspiration, and soil factors. The nonlinear type possesses lower radiation and/or less soil nutrients than the linear type, thereby suggesting that nonlinear type features higher degree of limitation from resources other than precipitation. This study suggests several factors limiting the responses of plant productivity to changes in precipitation, thus causing nonlinear NPP–precipitation pattern. Precipitation manipulation and modeling experiments should combine with changes in other climate and soil factors to better predict the response of plant productivity under future climate. [ABSTRACT FROM AUTHOR]

Responses of soil respiration (R s ) to increasing nitrogen (N) deposition and warming will have far-reaching influences on global carbon (C) cycling. However, the seasonal (growing and non-growing seasons) difference of R s responses to warming and N deposition has rarely been investigated. We conducted a field manipulative experiment in a semi-arid alfalfa-pasture of northwest China to evaluate the response of R s to nitrogen addition and warming from March 2014 to March 2016. Open-top chambers were used to elevate temperature and N was enriched at a rate of 4.42 g m − 2 yr − 1 with NH 4 NO 3 . Results showed that (1) N addition increased R s by 14% over the two-year period; and (2) warming stimulated R s by 15% in the non-growing season, while inhibited it by 5% in the growing season, which can be explained by decreased plant coverage and soil water. The main effect of N addition did not change with time, but that of warming changed with time, with the stronger inhibition observed in the dry year. When N addition and warming were combined, an antagonistic effect was observed in the growing season, whereas a synergism was observed in the non-growing season. Overall, warming and N addition did not affect the Q10 values over the two-year period, but these treatments significantly increased the Q10 values in the growing season compared with the control treatment. In comparison, combined warming and nitrogen addition significantly reduced the Q10 values compared with the single factor treatment. These results suggest that the negative indirect effect of warming-induced water stress overrides the positive direct effect of warming on R s . Our results also imply the necessity of considering the different R s responses in the growing and non-growing seasons to climate change to accurately evaluate the carbon cycle in the arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

Many uncertainties exist in our quest to understand and predict how terrestrial ecosystems will respond to climate change. A particularly challenging issue is how increases in extreme precipitation regimes, which are characterized by larger but fewer individual precipitation events, will impact ecosystems. Based on a wide-ranging review of empirical studies of both hydrological and ecological processes, Knapp et al. (2008) generated a suite of hypotheses positing how these processes would respond to an increase in extreme precipitation regimes and, from this, concluded that mesic ecosystems would be more detrimentally impacted than xeric ones. In this study we present the first thorough test of these hypotheses by examining how forest, shrubland, grassland and desert ecosystems of the Tibetan Plateau, having very different vegetation and climate characteristics, respond to more extreme rainfall regimes. We accomplished this by using a simulation model (Biome-BGC) to examine the integrated behavior of these ecosystems based on the simultaneous responses and interactions of 10 hydrological and ecological processes: runoff, canopy evaporation, soil evaporation, soil water storage, transpiration, net primary productivity, soil respiration, net ecosystem exchange, nitrogen [N] mineralization, and N leaching. We ran forty-year simulations (1986–2008) where we manipulated mean growing season precipitation to create more extreme intra-annual precipitation regimes characterized by lower precipitation frequencies, longer dry periods, and larger individual (daily) precipitation events. When compared to ambient conditions, our simulations showed that increases in extreme rainfall regimes (1) impacted all hydrological processes in mesic ecosystems, resulting in a reduction of soil mineral N due to increased leaching; and (2) enhanced plant growth in xeric ecosystems, leading to larger and denser canopies and higher light interception. The responses of hydrological processes tended to follow Knapp et al.’s hypotheses more so than ecological responses. Overall, responses of mesic ecosystems closely followed the hypotheses but xeric ecosystems were highly variable and only weakly consistent with them. Our findings provide new insights as to how more extreme rainfall regimes may potentially affect the functioning of terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Trend and variability of China's summer precipitation during 1955-2008 are examined. The results show that (1) summer precipitation has significantly increased in South China and significantly decreased in North China, while there are no significant trends in the West and China overall; (2) interannual variability is greatly intensified all over China with more wet and dry extreme years in the second bin (1977-2008) than in the first bin (1955-1976). Covariability between China's summer precipitation and the Pacific sea surface temperature ( SST) is analysed using singular value decomposition ( SVD) technique. The first mode of SVD displays an El Niño-Southern Oscillation ( ENSO)-like SST pattern, the associated precipitation shows negative anomalies in North China; the second mode exhibits SST fluctuations in the western and central Pacific that corresponding to positive anomalies in South China. In addition, cooling over the mid-lower reaches of Yangtze River basin (i.e. South-central China) might also contribute to decreased (increased) summer precipitation in North (South) China. The percentages of variance of summer precipitation and SST explained by each mode suggest that the increased variability of the second SVD mode in the second bin is consistent with intensified variability of China's summer precipitation in the same period. © 2013 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

We analyzed interannual variability (IAV) of precipitation and air temperature over a 40-year period (1969-2008) for 11 sites along a precipitation gradient on the Tibetan Plateau. The observed IAV for both precipitation and air temperature decreases with increasing mean annual precipitation. Using Biome-BGC, a process-based ecosystem model, we simulated net primary production (NPP) along this gradient and find that the IAV of NPP is positively correlated to the IAV of precipitation and temperature. Following projected climate change scenarios for the Tibetan Plateau, our simulations suggest that with increasing IAV of precipitation and temperature, the IAV of NPP will also increase and that climate thresholds exist that, if surpassed, lead to ecosystem die-off. The impacts of these changes on ecosystem processes and climate-vegetation feedbacks on the rapidly warming Tibetan Plateau are potentially quite significant. [ABSTRACT FROM AUTHOR]

Crossing certain aridity thresholds in global drylands can lead to abrupt decays of ecosystem attributes such as plant productivity, potentially causing land degradation and desertification. It is largely unknown, however, whether these thresholds can be altered by other key global change drivers known to affect the water-use efficiency and productivity of vegetation, such as elevated CO2 and nitrogen (N). Using >5000 empirical measurements of plant biomass, we showed that crossing an aridity (1–precipitation/potential evapotranspiration) threshold of ∼0.50, which marks the transition from dry sub-humid to semi-arid climates, led to abrupt declines in aboveground biomass (AGB) and progressive increases in root:shoot ratios, thus importantly affecting carbon stocks and their distribution. N addition significantly increased AGB and delayed the emergence of its aridity threshold from 0.49 to 0.55 (P  < 0.05). By coupling remote sensing estimates of leaf area index with simulations from multiple models, we found that CO2 enrichment did not alter the observed aridity threshold. By 2100, and under the RCP 8.5 scenario, we forecast a 0.3% net increase in the global land area exceeding the aridity threshold detected under a scenario that includes N deposition, in comparison to a 2.9% net increase if the N effect is not considered. Our study thus indicates that N addition could mitigate to a great extent the negative impact of increasing aridity on plant biomass in drylands. These findings are critical for improving forecasts of abrupt vegetation changes in response to ongoing global environmental change. [ABSTRACT FROM AUTHOR]

Background: Quantifying grassland aboveground biomass and soil nutrient removal in response to harvest intensities is essential to balance productivity and conservation benefit. There is a lack of studies examining the harvest frequency-induced threshold that leads to abrupt decay in grassland functioning. Methods: Based on field experiments in a semiarid and a dry subhumid grassland, we tested threshold responses of aboveground biomass (AGB) and removed plant nitrogen (N) and phosphorus (P) to 9-harvest frequency gradients within-year (2017 and 2018); and the legacy effects of harvest on AGB and soil available N and P pools and stoichiometry following cessation (2019) of harvest. Results: In both grasslands, the plant AGB within-year were highest at the frequency of ~2-harvest; it abruptly decreased once the threshold was exceeded. Moreover, except for plant N at the semiarid site, the response patterns of the N and P removals to harvest frequency were similar to that of plant AGB. The increased removal of N was higher than P with harvest frequency, leading to decreased soil available N/P ratio excess of twice at the dry subhumid site. Following cessation, the previous harvest frequency had a negative legacy effect on both plant AGB and the ratio of graminoid to forb species. Conclusions: These results indicate that ≤2-harvest annually are applicable for optimal pastoral production; among which one harvest by the end of the growing season may be appropriate for conserving above- and below-ground parts and maintaining healthy grassland functions. Soil N/P condition should be considered as an indicator when determining a sustainable harvest frequency. [ABSTRACT FROM AUTHOR]

Pasture-crop rotation has been considered as an efficient agronomical practice to improve soil and water conservation, develop livestock production, and promote food security. However, the characteristics of soil water restoration and performances of crop yield and water use efficiency (WUE) after conversion of long-term leguminous pasture into croplands still remain unclear. A field experiment was conducted in China's Loess Plateau to investigate soil water restoration and wheat yields in crop rotation with Italian ryegrass (Festuca perennis Lam.) and winter wheat (Triticum aestivum L.) converted from three 9-year-old leguminous pastures, viz. milk vetch (Astragalus adsurgens Pall.), alfalfa (Medicago sativa L.) and bush clover (Lespedeza davurica S.), and unplanted control (fallow). Soil water in the alfalfa treatment gradually recovered from up to down compared to the fallow treatment (control) during cultivation phase. After one year of rotation, the recovery levels of soil water in the three pasture-crop rotation systems at 0–500 cm soil depth were 97.1%, 95.5% and 94.2%, respectively, compared to the fallow treatment. The legume treatments significantly enhanced the crop yield (35.6%−64.5%), aboveground biomass (28.7%−59.4%) and WUE (60%−68.3%) of winter wheat compared with fallow. These results imply that the concerns about soil desiccation from long-term alfalfa was resolvable after long-term alfalfa converted into cropland in the rainfed farming area of Loess Plateau. The results also suggest that legume pasture-crop rotation can facilitate achieving a sustainable development of rainfed farming. • Soil water could be recovered after conversion of long-term leguminous pasture into cropland. • Fastest soil water restoration happened in alfalfa-crop rotation system with a top-down recovery pattern. • Legume pasture-crop rotation significantly increase wheat aboveground biomass and yield. [ABSTRACT FROM AUTHOR]

Deadly humid heat conditions exceeding human thermoregulatory capacity have been reported; however, whether and where the deadly humid heat events occur consecutively across the land surface are largely unknown. We calculate the maximum consecutive days of deadly humid heat, defined as daily maximum wet‐bulb temperature (TWmax) ≥35°C, for observations of 9,278 meteorological stations and for simulations of 14 global climate models. We further define short and long deadly humid heatwaves as a period of 3–4 and ≥5 consecutive days with daily TWmax ≥35°C, respectively. Our analyses show that six stations in some subtropical regions have experienced deadly humid heat with daily TWmax ≥35°C, but only occurs in individual days. Deadly humid heatwaves increase exponentially as the global mean temperature rising. When limiting global warming within 1.5°C, long deadly humid heatwaves will not occur across the land surface, and short deadly humid heatwaves will only emerge in some drylands but not in humid areas. Under 2°C warming, 0.09% of the global land, 0.42% of the human population, and 0.56% of the global centres of crop diversity are projected to be exposed to long deadly humid heatwaves. Meanwhile, 18% of the deadly humid heatwaves lasting ≥3 consecutive days will occur in humid areas; the fractions are projected to rapidly increase in humid areas as temperature rising further. At the end of the century, the percentage of land areas and human population exposed to deadly humid heatwaves lasting ≥3 consecutive days are expected to be 76‐times higher than that under 1.5°C warming level. Our finding suggests that keeping global warming within 1.5°C will significantly constrain the emergence of prolonged deadly humid heatwaves and thus reduce the risk of the human population especially outdoor agricultural workers. [ABSTRACT FROM AUTHOR]

Accurate long-term temperature and precipitation estimates at high spatial and temporal resolutions are vital for a wide variety of climatological studies. We have produced a new, publicly available, daily, gridded maximum temperature, minimum temperature, and precipitation dataset for China with a high spatial resolution of 1 km that covers a long-term period (1961 to 2019). It has been named the HRLT, and the dataset is publicly available at 10.1594/PANGAEA.941329 (Qin and Zhang, 2022). In this study, the daily gridded data were interpolated using comprehensive statistical analyses, which included machine learning methods, the generalized additive model, and thin plate splines. It was based on the 0.5 ∘ × 0.5 ∘ gridded dataset from the China Meteorological Administration, together with covariates for elevation, aspect, slope, topographic wetness index, latitude, and longitude. The accuracy of the HRLT daily dataset was assessed using observation data from meteorological stations across China. The maximum and minimum temperature estimates were more accurate than the precipitation estimates. For maximum temperature, the mean absolute error (MAE), root mean square error (RMSE), Pearson's correlation coefficient (Cor), coefficient of determination after adjustment (R2), and Nash–Sutcliffe modeling efficiency (NSE) were 1.07 ∘ C, 1.62 ∘ C, 0.99, 0.98, and 0.98, respectively. For minimum temperature, the MAE, RMSE, Cor, R2 , and NSE were 1.08 ∘ C, 1.53 ∘ C, 0.99, 0.99, and 0.99, respectively. For precipitation, the MAE, RMSE, Cor, R2 , and NSE were 1.30 mm, 4.78 mm, 0.84, 0.71, and 0.70, respectively. The accuracy of the HRLT was compared to those of three other existing datasets, and its accuracy was either greater than the others, especially for precipitation, or comparable in accuracy, but with higher spatial resolution or over a longer time period. In summary, the HRLT dataset, which has a high spatial resolution, covers a longer period of time and has reliable accuracy. [ABSTRACT FROM AUTHOR]

The microbial priming effect—the decomposition of soil organic carbon (SOC) induced by plant inputs—has long been considered an important driver of SOC dynamics, yet we have limited understanding about the direction, intensity, and drivers of priming across ecosystem types and biomes. This gap hinders our ability to predict how shifts in litter inputs under global change can affect climate feedbacks. Here, we synthesized 18,919 observations of CO2 effluxes in 802 soils across the globe to test the relative effects (i.e., log response ratio [RR]) of litter additions on native SOC decomposition and identified the dominant environmental drivers in natural ecosystems and agricultural lands. Globally, litter additions enhanced native SOC decomposition (RR = 0.35, 95% CI: 0.32–0.38), with greater priming effects occurring with decreasing latitude and more in agricultural soils (RR = 0.43) than in uncultivated soils (RR = 0.28). In natural ecosystems, soil pH and microbial community composition (e.g., bacteria: fungi ratio) were the best predictors of priming, with greater effects occurring in acidic, bacteria‐dominated sandy soils. In contrast, the substrate properties of plant litter and soils were the most important drivers of priming in agricultural systems since soils with high C:N ratios and those receiving large inputs of low‐quality litter had the highest priming effects. Collectively, our results suggest that, though different factors may control priming effects, the ubiquitous nature of priming means that alterations of litter quality and quantity owing to global changes will likely have consequences for global C cycling and climate forcing. [ABSTRACT FROM AUTHOR]

• Soil fungal community shifted from symbiotroph and saprotroph species towards pathotroph species with increased soil nutrients after two decades along a shrub plantation chronosequence. • Changes in microbial community composition and more fragmented network structure preceded the degradation of shrub physiology and biomass after 40 years. • A breakdown in soil microbial community structure can be an early warning sign of declines in shrub productivity and land degradation. Large-scale restoration is intended to promote ecological recovery. Improvements in plant and microbial conditions, however, may slow or even reverse in late succession. To better understand long-term restoration outcomes and underlying drivers of successional pathways, we tracked plant, bacterial and fungal, and soil conditions across a 40-year shrub plantation that was intended to stabilize desertified land in northern China. We found that planted Haloxylon ammodendron shrubs developed and then subsequently became degraded after 30–40 years. Bacterial abundance and α-diversity were much higher than those of fungi, but no significant differences in composition and structure were found in different plantation ages. In contrast, the dominant taxa of fungal communities shifted from symbiotroph and saprotroph species towards pathotroph species with increased soil nutrients in the plantation chronosequence after two decades. The changes in fungal dominant species led to a transition in microbial network structure and function, with an increase in negative linkages among taxa that began in the middle stages of succession. Changes in fungal community structure had direct and indirect negative effects on shrub leaf physiology, root activity, and biomass. Our results highlight the preceding role of a breakdown in soil microbial community composition and network structure on the degradation of shrub performance in long-term desert succession. Our study emphasizes the importance of understanding soil-microbial-plant linkages on restoration outcomes, and mechanisms that can slow or reverse the recovery of ecosystems. [ABSTRACT FROM AUTHOR]

Background and aims: In dryland regions, patches of vegetation play a crucial role in sequestering carbon and vital nutrients, creating what have been described as ‘fertile islands’ within the surface soil beneath their canopies. Nevertheless, a persistent question remains regarding the variability of fertile island effect in relation to soil depth.To investigate this, we sampled soils at two different depths (0–30 cm and 30–50 cm) within perennial vegetation patches and open areas across 54 drylands scattered across the Tibetan Plateau. Our study focused on six key soil variables related to carbon, nitrogen, and phosphorus stocks, allowing us to assess the differences in fertile island effects at varying depths.Among the soil fertility parameters evaluated, organic carbon exhibited the most pronounced fertile island effect at both soil depths. The fertile island effect responded differently to environmental factors at the two depths assessed. In the surface soil layer, the impact of vegetation on soil carbon content intensified with increasing precipitation seasonality and precipitation in the wettest quarter but declined with increasing temperature during the driest quarter. Conversely, in the deeper soil layer, the fertile island effect for nitrogen and phosphorus intensified with greater soil sand content and vegetation greenness.The fertile island effect can extend beyond the surface soil, while different environmental factors regulate the size of this effect with depth. These findings offer fresh and valuable insights into the relationships between biotic and abiotic factors and fertile island effects, a key feature of dryland ecosystems worldwide.Methods: In dryland regions, patches of vegetation play a crucial role in sequestering carbon and vital nutrients, creating what have been described as ‘fertile islands’ within the surface soil beneath their canopies. Nevertheless, a persistent question remains regarding the variability of fertile island effect in relation to soil depth.To investigate this, we sampled soils at two different depths (0–30 cm and 30–50 cm) within perennial vegetation patches and open areas across 54 drylands scattered across the Tibetan Plateau. Our study focused on six key soil variables related to carbon, nitrogen, and phosphorus stocks, allowing us to assess the differences in fertile island effects at varying depths.Among the soil fertility parameters evaluated, organic carbon exhibited the most pronounced fertile island effect at both soil depths. The fertile island effect responded differently to environmental factors at the two depths assessed. In the surface soil layer, the impact of vegetation on soil carbon content intensified with increasing precipitation seasonality and precipitation in the wettest quarter but declined with increasing temperature during the driest quarter. Conversely, in the deeper soil layer, the fertile island effect for nitrogen and phosphorus intensified with greater soil sand content and vegetation greenness.The fertile island effect can extend beyond the surface soil, while different environmental factors regulate the size of this effect with depth. These findings offer fresh and valuable insights into the relationships between biotic and abiotic factors and fertile island effects, a key feature of dryland ecosystems worldwide.Results: In dryland regions, patches of vegetation play a crucial role in sequestering carbon and vital nutrients, creating what have been described as ‘fertile islands’ within the surface soil beneath their canopies. Nevertheless, a persistent question remains regarding the variability of fertile island effect in relation to soil depth.To investigate this, we sampled soils at two different depths (0–30 cm and 30–50 cm) within perennial vegetation patches and open areas across 54 drylands scattered across the Tibetan Plateau. Our study focused on six key soil variables related to carbon, nitrogen, and phosphorus stocks, allowing us to assess the differences in fertile island effects at varying depths.Among the soil fertility parameters evaluated, organic carbon exhibited the most pronounced fertile island effect at both soil depths. The fertile island effect responded differently to environmental factors at the two depths assessed. In the surface soil layer, the impact of vegetation on soil carbon content intensified with increasing precipitation seasonality and precipitation in the wettest quarter but declined with increasing temperature during the driest quarter. Conversely, in the deeper soil layer, the fertile island effect for nitrogen and phosphorus intensified with greater soil sand content and vegetation greenness.The fertile island effect can extend beyond the surface soil, while different environmental factors regulate the size of this effect with depth. These findings offer fresh and valuable insights into the relationships between biotic and abiotic factors and fertile island effects, a key feature of dryland ecosystems worldwide.Conclusions: In dryland regions, patches of vegetation play a crucial role in sequestering carbon and vital nutrients, creating what have been described as ‘fertile islands’ within the surface soil beneath their canopies. Nevertheless, a persistent question remains regarding the variability of fertile island effect in relation to soil depth.To investigate this, we sampled soils at two different depths (0–30 cm and 30–50 cm) within perennial vegetation patches and open areas across 54 drylands scattered across the Tibetan Plateau. Our study focused on six key soil variables related to carbon, nitrogen, and phosphorus stocks, allowing us to assess the differences in fertile island effects at varying depths.Among the soil fertility parameters evaluated, organic carbon exhibited the most pronounced fertile island effect at both soil depths. The fertile island effect responded differently to environmental factors at the two depths assessed. In the surface soil layer, the impact of vegetation on soil carbon content intensified with increasing precipitation seasonality and precipitation in the wettest quarter but declined with increasing temperature during the driest quarter. Conversely, in the deeper soil layer, the fertile island effect for nitrogen and phosphorus intensified with greater soil sand content and vegetation greenness.The fertile island effect can extend beyond the surface soil, while different environmental factors regulate the size of this effect with depth. These findings offer fresh and valuable insights into the relationships between biotic and abiotic factors and fertile island effects, a key feature of dryland ecosystems worldwide. [ABSTRACT FROM AUTHOR]

Soil microbial communities regulate soil carbon feedbacks to climate warming through microbial respiration (i.e., metabolic rate). A thorough understanding of the responses of composition, biomass, and metabolic rate of soil microbial community to warming is crucial to predict soil carbon stocks in a future warmer climate. Therefore, we conducted a field manipulative experiment in a semiarid grassland on the Loess Plateau of China to evaluate the responses of the soil microbial community to increased temperature from April 2015 to December 2017. Soil temperature was 2.0°C higher relative to the ambient when open‐top chambers (OTCs) were used. Warming did not affect microbial biomass or the composition of microbial functional groups. However, warming significantly decreased microbial respiration, directly resulting from soil pH decrease driven by the comediation of aboveground biomass increase, inorganic nitrogen increase, and moisture decrease. These findings highlight that the soil microbial community structure of semiarid grasslands resisted the short‐term warming by 2°C, although its metabolic rate declined. [ABSTRACT FROM AUTHOR]

• Precipitation-lagged ecosystems in the Tibetan Plateau are more sensitive to biotic and environmental factors than unlagged ecosystems. • The precipitation regimes, instead of temperature and VPD, primarily drive the GPP variabilities in the Tibetan Plateau at the grid scale. • Precipitation might have a stronger impact on carbon uptake via variations in intra-distribution under future warming scenarios. Warming and precipitation variations have significant impacts on carbon uptake in the Tibetan Plateau. However, which climatic variable or process primarily drives the inter-annual variations of carbon uptake is not clear. Using multiple gross primary productivity (GPP) estimates, we study the controlling factors of the previous-year lagged effect and evaluate the effects of climate variables on GPP in the Tibetan Plateau. Results show that the lagged ecosystems in which productivity is significantly associated with previous-year precipitation are more sensitive to biotic and environmental factors than unlagged ones. In addition, previous-year precipitation as a whole has a positive impact on GPP over the Tibetan Plateau. Furthermore, precipitation regimes including precipitation intensity and dry-days fraction, and current-year precipitation amount primarily drive the GPP variabilities instead of temperature, vapor pressure deficit (VPD), and radiation at the grid scale. Future projections suggest that precipitation amount and intensity will increase, and dry-days fraction will decrease, which indicates that precipitation might have a more complicated impact on carbon uptake via variations in intra-distribution. Our study reveals the primary climatic factors that influence the variations of carbon uptake in the Tibetan Plateau, offering valuable insights for accurate carbon cycle modeling. [ABSTRACT FROM AUTHOR]

Abstract China initiated the "Grain for Green Project" in 1999 to mitigate soil erosion. The vegetation cover of the Chinese Loess Plateau, one of the most erosive regions in the world, has been greatly increased. However, studies on quantitatively investigating the climate change and human activities on vegetation coverage change were rare. In this study, spatio-temporal changes in vegetation coverage were investigated using MODIS normalized difference vegetation index (NDVI) data over 2000–2016. And a new method was introduced using Net Primary Productivity (NPP) model and relationship between NPP and NDVI to quantitatively and spatially distinguish the NDVI affected by climate change and human activities. Results showed that mean NDVI value over 2009–2016 were 14.46% greater than that over 2000–2007. In order to quantify the contribution of climate change and human activities to vegetation change, an NPP model suitable for the grassland of the Chinese Loess Plateau was identified using biomass observations from field survey and literature. The NDVI affected by climate change (NDVI climate) was estimated by the NPP model and the relationship between NPP and NDVI. And the NDVI affected by human activities (NDVI human) was calculated by actual NDVI minus NDVI climate. Comparison of the two stages showed that human activities and climate change contributed 42.35% and 57.65% respectively to the ΔNDVI on grassland in the Loess Plateau. After analysis of numerous NDVI human related factors, the slopes restored by the "Grain for Green Project" was considered the main influence factor of human activities. Graphical abstract Unlabelled Image Highlights • Novel method was developed to distinguish climate change and human activities. • Human activities contributed 42.35% to the vegetation change. • Climate change contributed 57.65% to the vegetation change. • The "Grain for Green Project" was the main human influence on vegetation. [ABSTRACT FROM AUTHOR]

Ridge-furrow mulching can reduce soil evaporation and conserve rainfall, thereby increasing crop yield and water use efficiency (WUE) in dryland cropping systems. In this study, we collected 837 observations from 50 published papers and used meta-analysis to investigate whether ridge-furrow and mulching practices are equally effective on maize yield, WUE and evapotranspiration (ET) across a range of precipitation and temperature gradients and soil types in China. Five practices were included: (i) straw mulch on flat plots (SMF), (ii) straw mulch on ridge-furrow plots (SMR), (iii) plastic mulch on flat plots (PMF), (iv) plastic mulch on ridge-furrow plots (PMR), and (v) flat plots without mulch, which was used as a control (CK). The meta-analysis showed that both straw mulch and plastic mulch significantly increased maize yields and WUE (except for SMR), and that plastic mulch was more effective than straw mulch in increasing yields, particularly in cold and dry environments. PMR has the highest yields and is more effective in clay loam than in silt loam soils. Straw mulch, but particularly plastic mulch, increased the soil moisture compared to the CK, while plastic mulch increased soil temperature, mainly in spring. However, the positive effect of plastic mulch on maize yield diminished with increasing mean growing-season temperature and precipitation, reaching zero (similar to the CK of no mulch and flat plots) when the growing-season precipitation was greater than 770 mm and the mean growing-season air temperature exceeded 24 °C. The small benefit of straw mulch (on average about 12%) was similar across the precipitation and temperature gradients, including when the benefits of plastic mulch reached zero. While our analysis has shown the benefits of ridge-furrow plastic mulch on yield and water-use efficiency, it has also highlighted the limitations of the benefits. The results provide a guide to the regions where plastic-film mulch and ridge-furrow planting are likely to improve maize yields and regions where the benefits are likely to be limited. [ABSTRACT FROM AUTHOR]

Evaluating the responses of soil respiration and its components to global environmental change is crucial for predicting future terrestrial carbon cycle. However, the effects of warming and nitrogen (N) addition on them remain unclear. A field manipulative experiment was conducted in a semi-arid grassland on the Loess Plateau to evaluate the responses of soil total respiration (Rt), autotrophic respiration (Ra) and heterotrophic respiration (Rh) to warming and N addition from April 2015 to December 2016. Open-top chambers were used to elevate temperature and N was added as NH 4 NO 3 at a rate of 4.42 g N m −2 yr −1 . Warming significantly decreased Rt and Rh by 7.4% and 9.5%, respectively, but had no significant effect on Ra. N addition significantly stimulated Ra by 34%, whereas it inhibited Rh by 11% and had no significant effect on Rt. The maximum N-inducing stimulation of Rt and Ra were observed in the month with the most rainfall events in 2015. N addition significantly increased the contribution of Ra to Rt by 10%. Warming decreased the Q10 values of Rt and Rh but had no significant effect on Q10 values of Ra. N addition significantly increased the Q10 values of Rt and Rh, whereas it decreased the Q10 values of Ra. The combination of warming and N addition had a synergistic effect on the cumulant of Rh, whereas it had an antagonistic effect on Ra. No interactive effect between warming and N addition was observed on Rt. Our results emphasized that Ra and Rh responded differently to warming and/or N addition, and the extreme rainfall frequency influenced the responses of Rt and its components to N addition. Our findings suggested that Rt has the potential to resist climate warming and increasing N deposition by differentiating the responses of its inherent components. [ABSTRACT FROM AUTHOR]

Purpose: In drought-prone soils, plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungus (AMF) might positively affect water uptake and crop yield via rhizosphere interactions.Sole and combined additions of Bacillus amyloliquefaciens producing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and Rhizophagus irregularis into rhizospheric soils were performed under well-watered (WW; 80% field water capacity), moderate water stress (MWS; 50% FWC) and severe water stress (SWS; 35% FWC) in pot-cultured wheat (Triticum aestivum L.).In moderate and severe drought stress, water use efficiency (WUEB) was increased by 27.9–34.3% in PGPR and 20–22.1% in AMF treatments, respectively, and grain yield was improved by 20.03–30.77% in PGPR and 12.13–34.34% in AMF treatments, respectively, compared with control (CK). Importantly, the co-inoculation of AMF and PGPR significantly promoted WUEB by 11.12–27.77% and grain yield by 18.26–21.68% compared to the average value of two sole inoculations in MWS and SWS treatments, respectively. WUEY and biomass production followed a similar trend as WUEB and yield. Particularly, the above parameters were significantly enhanced with the prolonged developmental stages (p < 0.05). ACC deaminase significantly reduced ACC accumulation in MWS and SWS, enhanced AMF root colonization, and promoted rhizosphere microbial biomass carbon and nitrogen levels across all three developing stages. Furthermore, AMF-PGPR co-inoculation enhanced chlorophyll and carotenoid contents during anthesis while reducing them during pre-harvesting. Enhanced water uptake and root activities upsurged photosynthetic traits throughout the growing season.AMF-PGPR co-inoculation acted as a promising solution to cope with the droughted environment via root activities for stronger water capture.Methods: In drought-prone soils, plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungus (AMF) might positively affect water uptake and crop yield via rhizosphere interactions.Sole and combined additions of Bacillus amyloliquefaciens producing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and Rhizophagus irregularis into rhizospheric soils were performed under well-watered (WW; 80% field water capacity), moderate water stress (MWS; 50% FWC) and severe water stress (SWS; 35% FWC) in pot-cultured wheat (Triticum aestivum L.).In moderate and severe drought stress, water use efficiency (WUEB) was increased by 27.9–34.3% in PGPR and 20–22.1% in AMF treatments, respectively, and grain yield was improved by 20.03–30.77% in PGPR and 12.13–34.34% in AMF treatments, respectively, compared with control (CK). Importantly, the co-inoculation of AMF and PGPR significantly promoted WUEB by 11.12–27.77% and grain yield by 18.26–21.68% compared to the average value of two sole inoculations in MWS and SWS treatments, respectively. WUEY and biomass production followed a similar trend as WUEB and yield. Particularly, the above parameters were significantly enhanced with the prolonged developmental stages (p < 0.05). ACC deaminase significantly reduced ACC accumulation in MWS and SWS, enhanced AMF root colonization, and promoted rhizosphere microbial biomass carbon and nitrogen levels across all three developing stages. Furthermore, AMF-PGPR co-inoculation enhanced chlorophyll and carotenoid contents during anthesis while reducing them during pre-harvesting. Enhanced water uptake and root activities upsurged photosynthetic traits throughout the growing season.AMF-PGPR co-inoculation acted as a promising solution to cope with the droughted environment via root activities for stronger water capture.Results: In drought-prone soils, plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungus (AMF) might positively affect water uptake and crop yield via rhizosphere interactions.Sole and combined additions of Bacillus amyloliquefaciens producing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and Rhizophagus irregularis into rhizospheric soils were performed under well-watered (WW; 80% field water capacity), moderate water stress (MWS; 50% FWC) and severe water stress (SWS; 35% FWC) in pot-cultured wheat (Triticum aestivum L.).In moderate and severe drought stress, water use efficiency (WUEB) was increased by 27.9–34.3% in PGPR and 20–22.1% in AMF treatments, respectively, and grain yield was improved by 20.03–30.77% in PGPR and 12.13–34.34% in AMF treatments, respectively, compared with control (CK). Importantly, the co-inoculation of AMF and PGPR significantly promoted WUEB by 11.12–27.77% and grain yield by 18.26–21.68% compared to the average value of two sole inoculations in MWS and SWS treatments, respectively. WUEY and biomass production followed a similar trend as WUEB and yield. Particularly, the above parameters were significantly enhanced with the prolonged developmental stages (p < 0.05). ACC deaminase significantly reduced ACC accumulation in MWS and SWS, enhanced AMF root colonization, and promoted rhizosphere microbial biomass carbon and nitrogen levels across all three developing stages. Furthermore, AMF-PGPR co-inoculation enhanced chlorophyll and carotenoid contents during anthesis while reducing them during pre-harvesting. Enhanced water uptake and root activities upsurged photosynthetic traits throughout the growing season.AMF-PGPR co-inoculation acted as a promising solution to cope with the droughted environment via root activities for stronger water capture.Conclusion: In drought-prone soils, plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungus (AMF) might positively affect water uptake and crop yield via rhizosphere interactions.Sole and combined additions of Bacillus amyloliquefaciens producing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and Rhizophagus irregularis into rhizospheric soils were performed under well-watered (WW; 80% field water capacity), moderate water stress (MWS; 50% FWC) and severe water stress (SWS; 35% FWC) in pot-cultured wheat (Triticum aestivum L.).In moderate and severe drought stress, water use efficiency (WUEB) was increased by 27.9–34.3% in PGPR and 20–22.1% in AMF treatments, respectively, and grain yield was improved by 20.03–30.77% in PGPR and 12.13–34.34% in AMF treatments, respectively, compared with control (CK). Importantly, the co-inoculation of AMF and PGPR significantly promoted WUEB by 11.12–27.77% and grain yield by 18.26–21.68% compared to the average value of two sole inoculations in MWS and SWS treatments, respectively. WUEY and biomass production followed a similar trend as WUEB and yield. Particularly, the above parameters were significantly enhanced with the prolonged developmental stages (p < 0.05). ACC deaminase significantly reduced ACC accumulation in MWS and SWS, enhanced AMF root colonization, and promoted rhizosphere microbial biomass carbon and nitrogen levels across all three developing stages. Furthermore, AMF-PGPR co-inoculation enhanced chlorophyll and carotenoid contents during anthesis while reducing them during pre-harvesting. Enhanced water uptake and root activities upsurged photosynthetic traits throughout the growing season.AMF-PGPR co-inoculation acted as a promising solution to cope with the droughted environment via root activities for stronger water capture. [ABSTRACT FROM AUTHOR]

• Leaf iWUE increases but ecosystem WUE decreases with aridity level. • iWUE and ecosystem WUE displayed almost opposite trends in response to abiotic factors. • MAT was the strongest factor in predicting iWUE, whereas the most robust factor in predicting ecosystem WUE was LAI. Water use efficiency (WUE) links carbon and water cycling and has been recognized as important in understanding the carbon-water budget of terrestrial ecosystems. However, there are few studies comparing WUE at leaf and ecosystem levels in response to environmental variables on a global scale. Here, we compare global-scale patterns and the drivers of leaf and ecosystem WUEs and quantify the relative influence of biotic and abiotic factors. Using published world-wide δ13C (carbon stable isotope composition) measurements for 6751 C 3 plant populations from 174 publications, as well as our own measurements of δ13C for 418 C 3 plant populations across drylands in China, and satellite-based datasets of gross primary production and evapotranspiration, we determined global patterns and the drivers of leaf and ecosystem WUEs. Leaf intrinsic WUE (iWUE) and ecosystem WUE displayed almost opposite trends, in response to abiotic factors on a global scale. iWUE was highest in arid regions and lowest in humid regions, whereas ecosystem WUE was lowest in arid regions and highest in humid regions. Phylogeny had a significant effect on iWUE. Mean annual temperature (MAT) was the strongest factor in predicting iWUE, whereas the most robust factor in predicting ecosystem WUE was leaf area index (LAI). The data indicate that the two different responses at the leaf and ecosystem levels must be considered when modeling carbon and water balances in response to climate change. [ABSTRACT FROM AUTHOR]

Lagged precipitation effect explains a large proportion of annual aboveground net primary productivity in some dryland ecosystems. Using satellite-derived plant productivity and precipitation datasets in the Northern Hemisphere drylands during 2000–2018, we identify 1111 pixels mainly located in the Tibetan Plateau, the western US, and Kazakhstan where productivities are significantly correlated with previous-year precipitation (hereafter, the lagged type). Differences in climatic and edaphic factors between the lagged and unlagged (pixels where productivities are not correlated with previous-year precipitation) types are evaluated. Permutational multivariate analysis of variance shows that the two types differ significantly regarding six climatic and edaphic factors. Compared to unlagged type, water availability, soil organic carbon, total nitrogen, field capacity, silt content and radiation are more sensitive to changes in precipitation in lagged type. Water availability is the most important factor for distinguishing the two types, followed by soil organic carbon, total nitrogen, field capacity, soil texture, and radiation. Our study suggests that the altered sensitivities of several climatic and edaphic factors to precipitation collectively affect the lagged effect of precipitation on productivity in drylands. Unlabelled Image • Climatic-edaphic factors differ significantly between lagged and unlagged drylands. • Lagged drylands were characterized by high sensitivity of water availability, SOC and nitrogen content to precipitation. • Water availability is the most important factor controlling lagged precipitation effect. [ABSTRACT FROM AUTHOR]

Precipitation is known to have legacy effects on plant diversity and production of many terrestrial ecosystems. Precipitation regimes are expected to become more variable with increasing extreme precipitation events. However, how previous-year precipitation regimes affect the current-year aboveground biomass (AGB) remains largely unknown. Here we measured long-term (2004–2017) AGB in a semi-arid grassland of the Chinese Loess Plateau to evaluate the impact of previous-year precipitation amount on current-year AGB. Furthermore, to assess the response of current-year AGB to previous-year precipitation regimes, we conducted a field manipulation experiment that included three precipitation regimes during 2014–2017: (i) ambient precipitation, (ii) monthly added four 5 mm rain events, and (iii) monthly added one 20 mm event. Both the long-term (2004–2017) observations under ambient precipitation and short-term (2014–2017) measurements under manipulative treatments showed significant positive effects of previous-year precipitation on current-year AGB. Our path analysis suggested that previous-year precipitation frequency had negative effects on the current-year density and mean height of grass (Leymus secalinus) while had positive effects on forb (Artemisia capillaris). The forb had much smaller height and AGB (65% and 53% less, respectively) than the grass. Consequently, the AGB reduced in the weekly small events treatment, causing the sensitivity of AGB to precipitation to decrease. Therefore, our findings indicated that the impacts of precipitation regimes on plant community dynamics should be taken into consideration while assessing the precipitation legacy effect on ecosystem production. Unlabelled Image • Current-year aboveground biomass (AGB) increased linearly with previous-year precipitation. • Precipitation frequency negatively affects the sensitivity of AGB to precipitation. • Previous-year precipitation amount increases the current-year grass density. • Previous-year precipitation frequency increases the current-year forb density. [ABSTRACT FROM AUTHOR]